The following is directed toward improved "track-following servo-mechanisms". A "track-following-servo" is a part of the servo-mechanism used in a disk file for head-positioning. Its function is to maintain the position of the recording heads exactly over the center of a selected disk track, with minimum displacement error, despite the presence of disturbances.
A major challenge in the design of a "track-following-servo" today is to maximize band-width and so minimize both "settling time" and "displacement errors"--while still assuring system stability and freedom from oscillations.